One of the most persistent issues in psychiatric epidemiology centers on social class: Are rates of some types of psychiatric disorder higher in lower social classes because of greater social stress; or are rates higher because genetically predisposed persons are selected into or fail to rise out of lower class environments? The long term goal of the present research is to use a quasi-experimental strategy to test these contrasting social stress-social selection explanations. The strategy involves comparisons of advantaged and disadvantaged ethnic groups with social class controlled, and tests of related predictions concerning group differences in the types and magnitudes of stressful life events experienced. The present study is a pilot study designed to determine the feasibility of implementing the quasi-experiment in Israel. There are two main reasons for this choice of research setting: First, the quasi-experimental strategy requires an open society in which ethnic assimilation is taking place. Second, study of the processes involved and their consequences can best be accomplished when a well kept Population Register and Psychiatric Register are available. Israel, probably uniquely, meets both sets of requirements. The long term goal is to compare relatively disadvantaged African and Asian Jews with relatively advantaged Jews of European origin in investigations of large samples of adult subjects. Comparisons would be made of true rates of schizophrenia, affective psychosis, antisocial personality, alcoholism or drug addiction, and neurosis, as well as for certain types of empirically derived symptom clusters. The measuring instruments would consist of the Psychiatric Epidemiology Research Interview (PERI) and Spitzer et al.'s SADS. The purpose of the present two year pilot study is to translate, test and calibrate these instruments which were developed in the United States in the different sociocultural setting of Israel. These tests are being conducted in interviews with 200 subjects sampled from different ethnic groups in Jerusalem and 240 psychiatric patients from the same ethnic groups.